Color television



Feb m 19%. P- DMARK 2,435,963

COLOR TELEVISION Filed Dec. 13, 1940 2 Sheets-Sheet 1 L 3% 5 a) 20 I5 NVE TOR Peter 60 9 72761)? ATTORNEYs Feh 9 194$ P. c. GOLDMARK COLOR TELEVISION Filed Dec. 15, 1940 2 Sheets-Sheet 2 INVENTOR .Pezer C 6oZdma/% BY Qua,

QM MVM ATTO R N EY$ Patented Feb. 17, 1 948 UNITED STATES PATENT OFFICE COLOR TELEVISION Peter 0. Goldmark, New York, N. Y., assignor. to Columbia Broadcasting System, Inc New York, N. Y., a corporation New York Application December-=13, .1940, s i-m at. 370,008

23 cl ims. (01. 178-54) 2' I This invention relates to television,v especially to recharge in accordance with another color to television in'natural colors. The invention aspect of the object field. This change prefer- .is particularly directed to the provision 01 'diably should take place progressively over the rect-pickup apparatus employing a transmitentire area of the image in phase with the moveting tube of the storage type. However, many ment of the scanning beam in the low-frequency features of the invention are more broadly apdirection. Since according to present seaming plicable. procedures an area is scanned from top to bot- At the present time, scanning devices of the tom or vice versa in a plurality of side-by-side storage type are commonly used for direct picklines, the present invention provides means up, that is, the scanning of natural object fields, w r y h @0101 y e changed alon either indcors or outdoors. as distinguished from straight line substantially Coincident wlth the film scanning. Non-storage tubes are suitable line b n s nn dfor film scanning, where adequate light can be In accordance with the present invention, a obtained, but are usually much less sensitive v ot -ting fi t drum having filter segments than storage type tubes and hence are not as ranged around its periphery is employed. The satisfactory for direct pickup. drum is preferably arranged in the path of light To televise pictures in color, a number of to the scanning device with the boundaries besystems have been suggested. In one type of tween segments substantially P el Optically system an object field is simultaneously scanned w t t lines of the image-receiving are?- which by a plurality of scanning devic in a n- 00 are scanned. The diameter and speed of rotasponding plurality of colors. The resulting tion of the drum and the number of filter segcolor signals are transmitted over separate chanments are advantageously selected 50 t t e nels to a receiver, where they are reproduced. boundaries between se e -trayerse t e In another type of system an object field is sucimage-receiving ar at substantially h s me cesslvely scanned in a plurality of primary colors 5 field scanning p e and fi scanning frequency and the corresponding signals sent over a. single as the scanning e Then. y pr pe ly Xmaschannel to a receiver. Commonly, a single scaning the drum with respect t the scanning nlng device is employed and diiierent color the boundaries between filter segments may be aspects of the object field are successively premade to substantially coincide w the e sented to the scanning devices, for example, by g scanned throughout the scanning 0f the a rotating tri-chromatic filter disk. This latter image- In this manner. the 6010i O e image type of system is considered preferable since it impinging on e lines nfthe scanning device avoids the difliculties and complexities of muls changed pr ressiv y as t li s a a tiple channel transmission and reception. thereby avoidingcolor carry-over from one field A difiiculty arises in connection with the use scansion to the next and enabling correct color of a storage tube and filter disk, namely, color rendition tn be Obtainedcarry-over from-one field scansion to the next. The invention Will be e fully e s od Ina storage tube the signal is built up throughy reference to the specific embodiments illusout all, or a large portion, of a field scanning petrated in the drawings and the following descripriod, and the signal thus stored up is released .t t e e at the instant of scanning. For example, in an In the drawings! electronic storage scanning device such as the l is a diagrammatic p ew st in so-called Orthicon or iconoscope," a light a specific embodiment of direct-pickup appaimage impinges on the image-receiving area fetus employing filter drum in ac ordance (commonly a mosaic target) and charges are with the invention;

stored up during the interval between succes- Fi -21s a from; view of the apparatus of Figsive scansions of a given portion of the area. Fig. 3 is adiagram illustrating he co ide ce As the scanning beam passes it discharges the between the boundary between filter se ment scanned areas, which thereupon begin to reand the line being sca e charge in accordance with the image then im- Fig. 4 is a diagram illustrating e u e 0! mi pinging on them. opaque strip between adjacent filters to avoid For correct color rendition it is desirable that color overlapping; and the color impinging on a given line of the mosaic Fig. 5 is an embodiment employing an intermebe changed as that line is scanned. In this diate image. manner as soon as a line is scanned it begins 68 Referring to Fig. 1, light rays from an object field it are collected by lens II and enter the open end l2 of the filter drum l3. Positioned inside the filter drum is a mirror I which diverts the light rays through the filters 22 located on the peripheral surface of the drum, and thence to the image receiving area l5 of a storage scanning device. Lens Ii focusses the rays to form an image l8 of the object fleld at the image-receiving area I5.

Any suitable type of storage scanning device may be employed, as desired. The tube specifically illustrated is of the Orthicon type, having an electron gun l1, horizontal deflecting plates l8, vertical deflecting coils l9 and axial field coil 2!. The horizontal deflecting plates and vertical deflecting coils are energized by suitable high-frequency and low-frequency sawtooth wave generators, as indicated. In the Orthicon, the image area I! is a translucent mosaic charge-storing target.

In the drum specifically illustrated, there are six filter segments 22 arranged around and forming the peripheral surface thereof, and comprise two sets of red, green and blue filters, denoted R, G and B (Fig. 2). Narrow strips 23 are provided between adjacent filter segments. These strips may be of any suitable material, such as brass, to which the filter segments may be secured. Instead of strips 23, other suitable means may be employed for securing the filter material to the surface of the drum. The boundaries between the filter segments, here formed by strips 23, extend laterally of the drum, and are advantageously parallel to the axis 24 of the drum. as shown. The drum is driven by motor 25 through suitable mechanical coupling means.

The speed of rotation of the drum is selected with respect to the number of filter segments so that thelsegments traverse the image receiving area at field scanning frequency. Proper synchronization may be obtained in ways known in the art. The'diameter oi the drum is advantageously selected in view of the number of sesments so that the boundaries between segments traverse the image-receiving area l5 in the lowfrequency direction (commonly the vertical direction) at substantially the same speed as that of the scanning beam in that direction. Then, by properly phasing the dmm with respect to the scanning beam, the boundaries between segments can be made to coincide with the lines being scanned as the scanning proceeds. The length of the segments in the axial direction will usually be sufiicient to include light rays of substantially the full length 01 the scanning lines.

In the embodiment of Fig. 1 the circumferential length of a given segment is approximately equal to the height of the image on area l5 plus an amount to allow for the blanking period,

' slightly modified by the optical magnification between the surface of the drum and the scanning area I5. The calculation of the actual dimensions will be clear to those in the art. With a uniform speed of rotation of the drum, the projection of the boundary onto the area will not move down the area at a precisely uniform speed. However, with a six-filter drum and a radius approximately equal to the image height, the departure from exact linearity does not exceed about. 1%. This variation will usually be quite permissible, but could be diminished by using a larger drum if desired.

Fig. 3 illustrates the coincidence of scanning and color changing. The scanning area I5 is scanned in horizontal side-by-side lines, it being assumed that scanning begins at the bottom and progresses toward the top. The position 01 the scanning beam at the instant under consideration is indicated by the dotted arrow 26. The dark band 21 represents the boundary between two adjacent filter segments, say, the red and green segments, as projected to the plane of the image. Prior to the passing Of the scanning beam 26, the lines of the image correspond to the red aspect of the object field, as indicated. Immediately after the passing of the scanning beam 26, the lines are exposed to the green aspect of the image, as indicated. Since the boundary between segments coincides substantially with the scanning beam, there is no color carryover from one field scansion to the next.

It will be understood that the boundary between adjacent segments will usually be wider at the scanning area than a scanned line, so that the boundary and line will not be coextensive. "Coincidence" as used herein hence refers to a condition where the boundary includes the line.

Although it is considered advantageous to have the boundary between adjacent segments coincide with the line being scanned as the scanning progresses, in some cases a small amount of color carry-over may be permissible. In such case, the drum need not be accurately phased with respect to the scanning beam, but may lead or lag somewhat. Usually the lead or lag of the beamwith respect to the boundary is advantageously small. so that substantial coincidence ensues.

Any suitable seaming system for scanning the area I5 may be employed as desired for example, either interlaced or non-interlaced. In the case oi electronic scanning devices employing a chargestoring mosaic, such as the Orthicon or iconoscope as at present constructed, it is found that a single scanning of the lines of the mosaic does not completely remove the charge on the lines. Thus, if the mosaic is exposed to an image-and the image cut oil, the lines may be scanned several times and corresponding signals of progressively decreasing magnitude developed during each scansion. The employment of bias light extending uniformly over the surface of the imagerecelving area has been found advantageous in many cases to produce a more pronounced decay between first and second scansions. Hence, the residual signal of one color aspect of the image will not seriously affect the signal corresponding to the next color aspect. The desired bias light may be obtained by the ring of small lights 2| positioned in front of the image-receiving area of the scanning tube. Bias light may of course be omitted if desired.

In the case of interlaced scanning of the area l5, when successive field scanslons correspond to different colors, color carry-over may result due to the fact that both sets of lines are exposed to one color, say red, but only one set of lines is scanned to obtain the red image signals. Both sets of lines are then exposed to the next color. say green, and the other set of lines scanned. However, since the latter set of lines will have been exposed to both the red and green aspect: of the image, correct color rendition may be seriously impaired. In such case it has been found advantageous to enlarge the diameter of the scanning spot somewhat so that the scanning 01' one line will discharge the adjacent lines, at least to some extent. This procedure will normally result in the loss of some detail, but the psychological effect of the addition of color to the image oil-v sets the decrease in detail.

Peter C. Goldmarir and John N. Dyer, Serial No. a

366,400, filed November 20, 1940. The filter drum of the present invention may be employed in connection with the image shifting disk disclosed in the aforesaid copending application.

the opaque band may be eliminated entirely, or made just wide enough to provide the required structural strength.

It will be observed that portions of the image area immediately adjacent the area. denoted G I: R receive rays from only afraction of the lens II when the portion of the filter plane between 32 and 33 is made substantially opaque.

Still further, only a single set of interlaced lines of the mosaic may be scanned during successive field scansions using a somewhat enlarged spot diameter, and the sets of lines reproduced at a receiver with normal interlacing and normal spot size. Some loss of detail will result, but will 5 be offset by the color.

In Fig. 1 the drum is positioned as close to the face of the scanning tube as possible, so that the boundaries between segments will be fairly sharp rays passing through adjacent filters of different color do not overlap on the image receiving area. In some cases this may not be feasible and it may be necessary to place the drum at such a 1y focussed on the image receiving area It. Thus,

distance from the image receiving area that the gs boundaries between filters are substantially out of focus at the image area, so that rays passing through adjacent filters of diiferent color may overlap at the image receiving area and cause undesirable color inter-mixture. the opaque bars 33 may be made suificiently wide to prevent such inter-mixture of colors.

Fig. 4 illustrates this efiect. In this More an object field III is focussed by lens Ii to form an In such case,

image It. Image it may be formed on the image 8 receiving area ii of the scanning tube as illustrated in Fig. 1. Irrthe path of the rays to the image area are shown two contiguous filter segments R and G, leaving a boundary line 30 therebetween. These filters may be taken to represent the surface of the drum l3 of Fig. 1 at some selected instant, with the filter segments contiguous rather than separated by the bars 23. As indicated in the figure, all light rays from point However, since the filters will be moving, all parts of the image area will receive substantially the same total illumination.

In some cases it may be necessary to place the drum so remote from the image receiving area that the use of an opaque band as shown in Fig. 4 will seriously restrict the total mount of light reaching the image receiving area during a field scanning period. In such case an intermediate image may be formed of the object field, the color drum placed at or near the intermediate image, and the resultant image of progressively changing color aspects Projected to the scanning device.

Referring to Fig. 5, an object field III is focussed by a first projection lens 3 to form an intermediate image 3Yat a, selected plane. The color filter drum I3 is positioned with the effective portion of its periphery at or near the plane of the intermediate image. After passing through the periphery of the drum the rays impinge on the mirror 14 which diverts the rays through the open end I! of the drum to a second projection lens 36. Lens 3! forms an image 31 of the intermediate image 38 at the image receiving area 38 of the scanning device, thereby rendering the intermediate plane and image area 38 conjugate to each other. Since the drum is at or near the intermediate plane, the boundaries will be substantially in focus at the image receiving area.

The scanning device is here shown as an electronic scanning tube 38 of the so-called icono scope type. In the conventional iconoscope the image receiving area 38 is a charge-storing mosaic which is positioned several inches away from the 28 in the object field pass through the green filter and impinge on the corresponding point 28' in the image field. Similarly, all light rays from point 29 in the object field pass through the red filter and impinge on the corresponding point 29' in the image field. Rays from all points between 28 and 29 in the object field will pass partly through the red filter and partly through the green filter before impinging on the image area,

as illustrated by the rays drawn from point 3! to the corresponding point 3|. v

There will thus be a band of mixed green and red in the image area, denoted G & R" in Fig. 4. This mixed band may be eliminated by rendering opaque the portion of the filter between points 32 and 33. Such an opaque band will cut oil all rays from all parts of lens H which pass through different filters before converging to a given point of the image field.

The proportions of Fig. 4 are exaggerated in order to illustrate more effectively the use of the opaque hand between filter segments. In a specific case. the width of the opaque band may be readily determined so as to cut oil the undesired rays without cutting of! more rays than are necessary. A small amount of intermixture may be permissible, in which case the opaque band may be made somewhat narrower than is required for the complete prevention of color intermixture.

If the filters are close enough to the image area, 1 allel optically" window ll of the tube. With such a tube the drum must necessarily be placed a considerable distance away from the image receiving area 38 and hence the use of an intermediate image with the filter drum placed at or near the plane of the intermediate image is advantageous. Of course, an iconoscope could be used in the single projection lens system in Fig. 1, if desired, particularly where a long focal length lens is employed. A field lens 42 maybe employed with advantage to direct the rays forming the intermediate image to the second projection lens 38.

Since the size of the intermediate image may be larger or smaller than that of the scanning device, the drum in Fig. 5 may be correspondthe scanning tube 39, rather than being parallel thereto as in Fig. 1. Nevertheless, the boundaries of the filter segments, although physically not parallel to the scanning lines of the scanning device, are optically parallel thereto because of the diverting of the light rays by mirror ll. It will be understood that when the term paris employed in the specification progressively with the scanning thereof.

with itsaxis parallel to the face of tube 38, as

in Fig. 1. In such case the intermediate image may be formed as the light rays leave the drum.

In Figs. 1 and the mirror I4 is at an angle of with respect to the axis of the drum, and the axis of the rays entering the drum are at right angles with respect to the axis of the rays leaving the drum. This angular relationship is advantageous in avoiding optical distortion. Nevertheless, if desired for any reason, the angular relationship may be otherwise. In such case. the optical relationships may be such that the boundary between a pair of filter segments is somewhat keystoned at the image receiving area. For example, in Fig. 5 if the mirror is at an angle of 60 with respect to the axis and the axial ray enters the drum-.perpendicular to the axis as shown, the axial exit ray will be at an angle with respect to the axis and consequently one end of the boundary between a given pair of segments may be magnified more than the other end with resultant keystoning at the image receiving area. In some cases such keystoning may not seriously adversely affect the operation of the apparatus. It will be understood that the term parallel optically" applies also to such a case.

In general it is desirable that the boundary of a filter segment at the image receiving plane be a straight edge moving down the image receiving area at the same speed and in coincidence with the line being scanned. However, departures from this relationship may be permissible in specific instances.

In Figs. 1, 2 and 5 the filter drum is circular in cross section. If desired, however, the filter segments may be flat rather than curved in which case the cross section would be hexagonal in shape for a drum having six segments. The number of segments may of course differ from that specifically illustrated.

The present invention has been developed for color television and is especially adapted thereto. However, many aspects of the invention are of broader application. The use of the drum in conjunction with a scanning device may be ad vantageous not only with color filter segments but also with segments of different optical characteristics generally, especially where it is de apparatus, and in receivers. The use of the drum in a receiver may be particularly advantageous with a receiver tube of the storage type or one having considerable after-glow, since the change from one filter to the next may be made to follow the scanning beam closely and all parts sired to change a'characteristic of the image The use of the opaque band and intermediate image may also be advantageous with such apparatus.

The features of an opaque band between segments of different optical characteristics, and an intermediate image with a rotatable element having segments of different optical characteristics at or near the plane thereof. may also be useful in connection with rotatable elements or devices other than drums, for example, disks. Both the opaque band and intermediate image may be employed in a single apparatus, if desired.

Although the invention is particularly directed to direct pick-up apparatus employing storage tube, the invention can also be employed in other apparatus, for example, in connection with non-storage scanning devices, in film-scanning of the image area may be exposed through a given segment for equal intervals.

Many modifications of the apparatus of the invention may be made by those skilled in the art without departing from'the spirit and scope of the invention.

Iclaim:

1. In color television apparatus, the combination which comprises an electronic scanning device, means for scanning an image area with said scanning device in two dimensions in a plurality of side-by-side lines, a rotatable color-filter drum having a plurality of color-filter segments of diflerent optical characteristics arranged around the peripheral surface thereof, said drum being positioned and arranged in the path of the image light of said image area with the boundaries between segments substantially parallel optically with said lines of the image area, and said light passing through said segments as the drum rotates with progressive change of color at substantially the same speed at which the lines are scanned.

2. In color television apparatus, the combination which comprises an electronic scanning device. means for scanning an image area with said scanning device in two dimensions in a plurality of side-by-side lines, a rotatable colorfilter drum having a plurality of color-filter segments of diflerent optical characteristics arranged around the peripheral surface thereof with the boundaries between segments substantially parallel to the axis of the drum, said drum being positioned and arranged in the path of the image light of said image area with the boundaries be-' tween segments substantially parallel optically with said lines of the image area and said light passing through said segments as the drum rotates with progressive change of color at substantially the same speed at which the lines are scanned, the length of the segments in the axial direction being sufllcient to include light rays of substantially the full length of said lines.

3. In color television apparatus, the combination which comprises an electronic scanning device, means for scanning an image area with said scanniig device in two dimensions in a plurality of side-by-side lines, a rotatable color-filter drum having a plurality of color filter segments arranged aroundthe peripheral surface thereof with laterally extending boundaries therebetween, said drum being positioned and arranged in the path of the image light of said imag area with the boundaries between segments substantially parallel optically with said lines of the image area and said light passing through said segments as the drum rotates with progressive change of color at substantially the same speed at which the lines are scanned, the length of the segments in the axial direction being suflicient to include light rays of substantially the full length of said lines.

4. In color television apparatus, the combination which comprises an electronic scanning device of the storage type having an image area associated therewith, means for scanning said image area in two dimensions in a plurality of side-by-side lines, a rotatable color-filter drum having a plurality of color-filter segments of assumes different optical characteristics arranged around the peripheral surface thereof with boundaries substantially parallel to the axis of the drum. said drum being positioned and arranged in the path of the image light of said image area with said boundaries substantially parallel optically with said lines of the image area, the length of the segments in the axial direction being sufiicient to include light rays of substantially the full length of said lines, and means for rotating said drum in substantial synchronism with the low frequency scanning of said image area to cause said boundaries to traverse the image area in substantial synchronism with the scanning of said lines, said drum being arranged so that said light passes through the segments successively as the drum rotates and the circumferential extent of a segment being sufilcient to include light of a substantial proportion of said lines when said segment is in operating position.

5. In color television apparatus, the combination which comprises an electronic scanning device of the storage type having an image area associated therewith, means for scanning said image-area in two dimensions in a plurality of side-by-side lines, a rotatable color-filter drum having a plurality of color filter segments arranged around the peripheral surface thereof with laterally extending boundaries, said drum being positioned and arranged in the path of the image light of said image area with the boundaries between segments substantially parallel optically with said lines of the image area so that as the drum rotates the filter segments are successively interposed in the path of said image light, the length of the segments in the axial direction being sufllcient to include light rays of substantially the full length of said lines, and means for rotating said drum in substantial synchronism with the low frequency scanning of said image area to cause said boundaries to traverse the image area in substantial synchronism with the scanning of said lines, said drum being arranged so that said light passes through the seg-. ments successively as the drum rotates and the circumferential extent of a segment being sufficient to include light of a substantial proportion of said lines when said segment is in operating position. c

6. In color television transmitting apparatus, the combination which comprises an electronic storage scanning device having an image-receiving area associated therewith, means for focusing a two-dimensional light image of an object field on said image-receiving area, means for scanning an image on said image-receiving area in two dimensions in a plurality of side-by-side lines, a rotatable color-filter drum having a plurality of color-filter segments of diflerent optical characteristics arranged around the peripheral surface thereof with laterally extending boundaries, said drum being positioned and arranged in the path of light rays forming said image with the boundaries between segments as projected to said image-receiving area substantially parallel with said lines as the projections of the boundaries traverse said area, the length of the segments in the axial direction being sufllcient to include light rays of substantially the full length of said lines, and means for rotating said drum in substantial synchronism with the low frequency scanning of said image area to cause said boundaries to traverse the image area in substantial synchronism with the scanning of said lines. said drum being arranged so that said light passes through the segments successively as the drum rotates with progressive change of color at substantially the same speed at which the lines are scanned. and the circumferential extent of a segment being sufiicient to include light of a substantial proportion of said lines when said segment is in operating position.

'7. In color television transmitting apparatus, the combination which comprises an electronic scanning device of the storage type having an image-receiving area associated therewith, means for focusing a two-dimensional light image of an object field on said image-receiving area, means for scanning an image on said image-receiving area in two dimensions in a plurality of side-byside lines, means for progressively changing the color aspect of said light image including a rotatable color-filter drum having a plurality of color filters arranged around the peripheral surface thereof with laterally extending boundaries therebetween, said drum being positioned and arranged in the path of light rays forming said image with the boundaries between said filters substantially parallel optically with said lines, and means for rotating said drum in substantial synchronism with the low frequency scanning of said image area to cause said boundaries to substantially coincide with the line being scanned as the boundaries successively traverse the imagereceiving area, said drum being arranged so that said light passes through the filters successively as the drum rotates with progressive change of color at substantially the same speed at which the lines are scanned, and the circumferential extent of a filter being sufficient to include light of a substantial proportion of said lines when said filter is in operating position.

8. In color television transmitting apparatus, the combination which comprises an electronic scanning device of the storage type having an image-receiving area associated therewith, means for focusing a two dimensional light image of an object field on said image-receiving area, means associated with' said scanning device for scanning an image on said image-receiving area in two dimensions in a plurality of side-by-side lines at a selected field-scanning frequency, a rotatable color-filter drum having a plurality of color filters arranged around the peripheral surface thereof with laterally extending boundaries therebetween, said drum being positioned and arranged in the path of light rays forming said image with the boundaries between said filters substantially parallel optically with said lines so that as the drum rotates the color impinging on said lines is progressively changed over the image-receiving area, light of the colors of ad- :Iacent filters impinging on adjacent areas of the image-receiving area as the boundary therebetween traverses the image-receiving area, and means for rotating said drum so that said boundaries traverse the image-receiving area at field scanning frequency and at substantially fieldscanning speed with said boundariessubstantially coinciding with the line being scanned as the boundaries successively traverse the image-receiving area, said drum being arranged so that said light passes through the filters successively as the drum rotates and the circumferential extent of a filter being suflicient to include light of a substantial proportion of said lines when said filter is in operating position.

9. In color television transmitting apparatus. the combination which comprises an electronic scanning device of the storage type having an image-receiving area associated therewith, means for focusing a two-dimensional light image of an object field on said image-receiving area, means associated with said scanning device for scanning an image on said image-receiving area in two dimensions in a plurality of side-by-side lines at a selected field-scanning frequency, a rotatable drum having a plurality of transparent color filter segments arranged around the peripheral surface thereof with the boundaries between filters substantially parallel with the drum axis, a mirror within said drum, said drum and mirror being positioned and arranged in the path of light rays forming said image to cause said light rays to pass through part of the periphery and one end of the drum, the boundaries between said filters being substantially parallel optically with said lines so that as the drum rotates the color impinging on said lines is progressively changed over the image-receiving area, light of the colors of adjacent filters impinging on adjacent areas of the image-receiving area as the boundary therebetween traverses the image-receiving area, and means for rotating said drum so that said boundaries traverse the scanning area at fieldscanning frequency and at substantially fieldscanning speed with said boundaries substantially coinciding with the line being scanned as the boundaries successively traverse the image-receiving area, the circumferential extent of each segment being suflicient to include light rays of a substantial proportion of said lines when the segment is in operating position.

10. In color television transmitting apparatus, the combination which comprises an electronic scanning device having an image-receiving area associated therewith, means for focusing a twodimensional image of an object field at a selected intermediate plane, means for focusing an image at said intermediate plane on said image-receiving area of the scanning device, means for scanning an image on said image-receiving area in two dimensions in a plurality of side-:by-side lines, and a rotatable color-filter drum having a plurality of color-filter segments of diiierent optical characteristics, said rotatable color-filter drum being positioned near said intermediate plane so that said plurality of segments are successively interposed in the path of the image light rays with the boundaries between segments traversing the image area in a direction transverse to said lines with progressive change of color at substantially the same speed at which the lines are scanned. whereby an optical characteristic of an image impinging on said image-receiving area may be progressively changed at a position remote from said area with the boundaries between segments substantially in focus at said area.

11. In color television transmitting apparatus, the combination which comprises an electronic scanning device of the storage type having an image-receiving area associated therewith, means for focusing a two-dimensional light image of an object field at a selected intermediate plane, means for focusing an image at said intermediate plane on said image-receiving area of the scanning device, means associated with said scanning device for scanning an image on said image-receiving area in two dimensions in a pluralit of side-by- 70 side lines at a selected field-scanning frequency, a rotatable drum having a plurality of transparent color filters arranged around the peripheral surface thereof with laterally extending boundaries therebetween,

said drum being positioned 1b nd ed in the path of the light rays near said intermediate plane so that the boundaries are substantially in focus at said image-receiving area as the boundaries traverse the area, the boundaries being substantially parallel optically with said lines of the image-receiving area so that as the drum rotates the color impinging on the lines is progressively changed over the imagereceiving area, light of the colors of adjacent filters impinging on adjacent areas of the imagereceiving area as the boundary therebetween traverses the image-receiving area, and means for rotating said drum so that said boundaries traverse the image-receiving area at field-scanning frequency and at substantially field-scanning speed with said boundaries substantially coinciding with the line being scanned as the boundaries successively traverse the image-receiving area, the circumferential extent of each segment being suflicient to include light rays of a substantial proportion of said lines when the segment is in operating position.

12. A color television signal-translating system comprising, a cathode-ray tube including a target, means for successively scanning said target with an electron beam in a series of parallel lines, color-filter-carrying means interposed in the optical path between said target and the television, image to be translated, means for moving said filter-carrying means so that the lines of color demarcation thereof remain substantially parallel to said lines of said series for changing the color of light associated with each line a predetermined interval after such line is scanned and for maintaining said color associated with said line until said line is next scanned by said beam, and means for blocking the image of each line during the interval said line is being scanned.

13. In a television system adapted to generate and transmit signals representative of images in natural colors a tube having a charge storage electrode and means to develop an electron beam, a movable filter comprising a plurality of filter segments adapted to move sequentially and transmit to said electrode light representative of individual colors from an object of which colored image representations are to be transmitted, means to move said filter at a predetermined rate to expose successive areas of said electrode to colored image components of said object, means to scan the electron beam of said tube over a portion of said electrode in the direction and at the predetermined rate of exposure of said colored image components while other portions of said electrode are illuminated by a differently colored light image component of said object, and means to maintain the said portion of said electrode being scanned by said beam unilluminated by light from said object whereby the signal derived as a result of said electron beam scanning is representative at any one time of only one color of light projected on said electrode.

14. In color television apparatus, the combination which comprises an electronic scanning device, means for scanning an image area with said scanning device in two dimensions in a plurality of side-by-side lines, a rotatable color-filter assembly having a plurality of color-filter segments of different optical characteristics, said assembly being positioned and arranged in the path of the image light of said image area with the boundaries between segments substantially parallel optically with said lines of the image area and said light passing through said segments as the assembly rotates with progressive change of color ensues 13 at substantially the same speed at which the lines are scanned.

15. A color television transmitting system including a transmitting tube having a light responsive electrode, means in said tube for generating a focused beam of electrons, means for deflecting the beam in horizontal and vertical directions at different rates in order to cyclically scan the light responsive electrode, a lens system for projecting an optical image on the light responsive electrode, a color filter assembly having a plurality of filters of different colors, means for moving the color filter so that a diiferently colored filter is interposed in the optical axis for each vertical deflection cycle of the cathode ray beam to produce a succession of differently colored images on said electrode, and means to synchronize the movement of said color filter with the vertical deflection cycle of saidbeam to cause said beam to scan a progressively moving area of said electrode adjacent the junction of two differently colored images 'on said electrode.

16. In a television transmitting system for transmitting signals representative of a colored optical image including a cathode ray tube having a light responsive target electrode adapted to receive an image of an object of which a picture is to be transmitted and electron beam generating means. a light filter assembly including a plurality of filters, adjacent filters being capable of transmitting light of different colors, means to project light from an object through the filters of said filter assembly and upon said target electrode, means to move said filter assembly to produce a succession of colored images of the object on said electrode and means to scan said target electrode by the generated electron beam synchronously with the movement of said filter assembly and over an area of said electrode adjacent two diflerently colored images projected on said electrode through adjacent filters of said filter assembly.

17. In a television transmitting system for transmitting signals representative of color image fields. a signal generating tube including a, light sensitive electrode adapted to receive an optical image over the extended surface thereof, and electron beam generating means. a filter assembly including a plurality of differently colored light filters adapted to intercept a portion of light from an object of which an image is to be transmitted, said filters being separated by portions opaque to white light, means to move said filter assembly to subject Said electrode to light from said object in successively diflerent colors separated by one of said opaque portions, and means synchronized and phased with said last-mentioned means to scan the generated electron beam over said electrode over a progressively moving area in the shadow cast on said electrode by said opaque portion to develop signals representative in intensity to the illumination of a single color of light.

18. In color television transmitting apparatus, the combination which comprises an electronic scanning device of the storage type having an image-receiving area associated therewith, optical means positioned to focus a two-dimensional light image of an objectfield onto said image-receiving area, scanning means associated with said scanning device for scanning said image in two dimensions in a lurality of side-by-side lines, a rigid rotatable color-filter assembly having a plurality of color-filter segments of different optical characteristics, said assembly being positioned and arranged in the path of lisht from said optical means to said image-receiving area with said color-filter segments traversing the image light near said area, the boundaries between color-filter segments being substantially parallel optically with said scanning lines as the boundaries traverse the image-receiving area and said light passing through said segments as the assembly rotates with progressive change of color at substantially the same speed at which the lines are scanned.

19. In color television transmitting apparatus, the combination which comprises an electronic scanning device of the storage type having an image-receiving area associated therewith, optical means positioned to focus a two-dimensional light image of an object field onto said imagereceiving area, scanning means associated with said scanning device for scanning said image in two dimensions in a plurality of side-by-side lines.

. a rigid rotatable color-filter assembly having a plurality of color-filter segments of different optical characteristics spaced there-around with substantially opaque boundaries therebetween,

said assembly being positioned and arranged in the path of light from said optical means to said image-receiving area with said color-filter sesments traversing the image light near said area. the boundaries between color-filter segments being substantially parallel optically with said scanning lines as the boundaries traverse the imagereceiving area and said light passing through said segments successively as the assembly rotates. and driving means for rotating said assembly in substantial synchronism with the low-frequency scanning of said image with said boundaries substantially coinciding with the lines being scanned as the boundaries successively traverse the imagereceiving area.

20. In color television transmitting apparatus. the combination which comprises an electronic scanning device of the storage type having an image-receiving area substantially at the front end thereof, a single lens positioned to focus a two-dimensional light image of an object field directly onto said image-receiving area, scanning means associated with said scanning device for scanning said image in two dimensions in a plurality of side-by-side lines, a rigid rotatable color-filter assembly having a plurality of colorfilter segments of difierent optical characteristics spaced therearound with substantially opaque boundaries therebetween, said assembly being positioned and arranged with said color-filter segments traversing the image light closely adjacent to said image-receiving area, the boundaries between color-filter segments being substantially parallel optically with said scanning lines as the boundaries traverse the image-receiving area and said light passing through said segments successively as the assembly rotates, and driving means for rotating said assembly in substantial synchronism with the low-frequency scanning of said image with said boundaries substantially coincldlng with the lines being scanned as the boundaries successively traverse the image-receiving area. p

21. In color television transmitting apparatus, the combination which comprises an electronic scanning device or the storage type having an image-receiving area associated therewith, optical means positioned to focus a two-dimensional light image of an object field onto said imagereceiving area, scanning means associated with said scanning device for scanning said image in two dimensions in a plurality of side-by-side lines as the boundaries traverse the image-rej ceiving area and said light passing through said segments as the assembly rotates with progressive change of color at substantially the same speed at which the lines are scanned, said boundaries being sufilciently wide to substantially prevent image light to any point of the image-receiving area from simultaneously passing through adjacent filter segments of different optical characteristics.

22. In color television transmitting apparatus, the combination which comprises an electronic scanning device of the storage type having an image-receiving area associated therewith, a single lens positioned to focus a two-dimensional light image of an object field directly onto said image-receiving area, scanning means associated with said scanning device for scanning said image in two dimensions in a plurality of side-by-side lines; a rigid rotatable color-filter assembly having a plurality of color-filter segments of different optical characteristics spaced therearound with substantially opaque boundaries therebetween, said assembly being positioned and arranged in the path of light from said optical means to said image-receiving area with said opaque boundaries out of focus at said area, the boundaries between color-filter segments being substantially parallel optically with said scanning lines as the boundaries traverse the image-receiving area and said light passing through said segments successively as the assembly rotates, and driving means for rotating said assembly in substantial synchronism with the low-frequency scanning of said image with said boundaries substantially coinciding with the lines being scanned as the boundaries successively traverse the image-receiving area, said boundaries being suffleiently wide to substantially prevent image light to any point of the image-receiving area from simultaneously passing through adjacent filter segments of difierent optical characteristics.

23. In color television transmittingapparatus, the combination which comprises an electronic scanning device of the storage type having an image-receiving area associated therewith, means for focussing a two-dimensional light image 01' an object field on said image-receiving area, means for scanning an image on said image-receiving area in two dimensions in a plurality of side-by-side lines, means for progressively 5 changing the color aspect of said light image including a rotatable color-filter drum having a plurality of color filter segments arranged around the peripheral surface thereof with laterally extending substantially opaque boundaries therebetween, said drum being positioned and arranged in the path of light rays forming said images with the boundaries between said filters substantially parallel optically with said lines and substantially out of focus at said image-receiving area, and means for rotating said drum in substantial synchronism with the low frequency scanning of said image to cause said boundaries to substantially coincide with the line being scanned as the b'oundaries successively traverse the image-receiving area, said drum being arranged so that said light passes through the filter segments successively as the drum rotates with progressive change of color at substantially the same speed at which the lines are scanned, the circumferential extent of a filter segment being sufficient to include light of a substantial proportion of said lines when said segment is in operating position and said boundaries being suiliciently wide to substantially prevent image light to any point of the image-receiving area lrom simultaneously passing through adjacent filter segments 0! difierent color.

PETER C. GOLDMARK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,173,476 Goldmark Sept. 19, 1939 2,059,222 Fessenden Nov. 3, 1936 1,844,508 Jenkins Feb. 9, 1932 2,196,130 Urtel Apr. 2, 1940 1,988,303 Donle Jan. 15, 1935 1,859,824 Godefroy May 24, 1932 2,010,307 Leishman Aug. 6, 1935 1,137,320 Hochstetter Apr. 27, 1915 937,367 Friese-Greene Oct. 19, 1909 1,399,567 Lehman Dec. 6, 1921 2,221,091 Goldsmith Nov. 12, 1940 FOREIGN PATENTS Number Country Date 377,187 Great Britain July 13, 1932 473,323 Great Britain Oct. 11, 1937 391,781 Great Britain May 2, 1933 

